Wide band antenna response is often required to meet the demands of portable communication equipment which may use an 800 or 900 MHz carrier frequency, a GPS locator (which can operate at the GPS carrier frequencies in the L band in the frequency range between 1227.6 MHz and 1575.42 MHz), and may also talk with other devices over Bluetooth or WLAN frequencies which can range around 2.4 GHz. This multi-band requirement often leads to multiple antenna solutions with increased cost, increased complexity but lower reliability.
Most antennas used in wireless handset communications are wire whips, coils or sheets of metal such as planar inverted-F antennas (PIFA). These are relatively narrow band devices covering a range of about 10% of the bandwidth required. There is also a new class of related antennas known as conductive plastic antennas which attempt to generate the radiating fields within the plastic itself. The problem with the conductive plastic antennas is that the cheapest polymers or most commercially available plastics are themselves lossy and absorb much of the radiated energy especially at higher frequencies. An example of such an antenna including conductive plastic is discussed in U.S. Pat. No. 6,741,221 by Thomas A. Aisenbrey which describes “conductive loaded resin-based materials” used for the radiating antenna and the counterpoise antenna elements. No single existing antenna provides sufficient wideband performance while having minimal dielectric losses for the multi-band requirements of communication devices found today.